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A methodology for using the estuarine grass shrimp (Palaemonetes pugio) in life-cycle toxicity tests was successfully developed.
Life-cycle exposures of juvenile shrimp (12 to 19 mm in rostrum-telson length) to the chlorinated hydrocarbon pesticide endrin were begun in November 1976 and completed in March 1977. After the juveniles matured and spawned, the effects on their progeny were determined. Tests were conducted in a flow-through seawater system, using a modified Mount and Brungs diluter. The average measured exposure concentrations were 0 (control), 0.03, 0.05, 0.11, 0.18, 0.38, and 0.79 µg endrin/litre seawater.
The juveniles reached sexual maturity during the first two weeks of the exposure. Thereafter, a photoperiod regime was used to induce reproduction, and the effects of endrin on the survival, growth, and reproduction of the parent generation were determined. Larvae spawned by control and exposed parents were continuously exposed until the juvenile stage (7 to 20 mm in rostrum-telson length). The effects on survival, length of larval development, and growth of the F1 generation were determined.
The 96-h LC50 for juvenile grass shrimp was 0.35 µg endrin/litre water. In the life-cycle toxicity test, gonadal development and spawning were inhibited at 0.03 µg endrin/litre water. Because this was the lowest concentration tested, the maximum allowable toxicant concentration could not be determined. The specific application factor for grass shrimp is, therefore, less than 0.08, approximately one order of magnitude lower than those generated in life-cycle tests exposing freshwater and estuarine fishes to endrin.
toxicology, toxicity tests, endrin, life cycles, application factor, aquatic toxicology
Research biologist, Environmental Research Laboratory, U.S. Environmental Protection Agency, Gulf Breeze, Fla.